Aperture cover and method of making the same

ABSTRACT

The method of producing the aperture cover wherein the parts being integrated are disposed in juxtaposed position followed by a time phased application of a force pulse and an electrical energy pulse to the assembled parts to produce a solid state resistance weld at the faying interface.

United States Patent Anderson 1 July 1 1, 1972 [54] APERTURE COVER ANDMETHOD ()1? 2,287,540 6/1942 Vang ..219/117 X MAKING THE SAME 3,067,32012/1962 Muir ..219/9l X 3,113,202 12/1963 Molen et al. ....2l9/l 17 RlnvemorI as": m n, Bloomfield H Rl5,46 6 10/1922 Murray, .Ir. ..219/1 17R Primary Examiner-J. V. Truhe 73 A to W I sslgnee Qua Company Troy MichAssistant Exammer-Gale R. Peterson Filed: M 1970 Attorney-Wilson &Fraser [21] Appl. No.: 80,921

ABS'I'RA [52] U.S.Cl. ..2l9/l17R,219/86,219/91, [57] CT 1 219/107 Themethod of producing the aperture cover wherein the parts [51] Int. Cl.3231; 11/04 being integrated are disposed in juxtaposed positionfollowed [58] Field of Search ..2 19/1 17 R, 91, 85, 86, 1 19 by a timephased application of a force pulse and an electrical energy pulse tothe assembled parts to produce a solid state re- [56] References Citedsistance weld at the faying interface.

UNITED STATES PATENTS 7 Chins, 6 Drawing figures 3,435,181 3/1969 Walkow..2l9/91 FORCE MECHANISM POWER SUPPLY FORCE POWER SWITCH SHEET lUF 2INVENTOR. DAVID c. ANDERSON BY MM 1 ATTORNEYS P'ATENTEDJHL 1 1 1972PATENTEDJUL 11 m2 3575637 sum 2 n; 2

Ill W In,

' INVEN R. DAVID c. ANDER N ATTORNEYS APERTURE COVER AND METHOD OFMAKING THE SAME BACKGROUND OF THE INVENTION In the manufacturing processfor producing engine blocks for use in internal combustion engines, theinternal passageways for the conduction of lubricating fluids throughthe completed engine may be formed by drilling. The drilled passagewaystraverse the entire length of the block and may intersect with othercavities or drilled holes to conduct the lubricating fluid. The drilledpassageways that traverse the entire length of the engine block areknown as galley holes." Since the lubricating fluids would escapethrough the galley holes during engine operation, the holes must beadequately sealed. Two principal methods are utilized for sealing thegalley holes. One of the methods involves the use of a relatively softmetal plug which is merely forced into tight engagement in the holes bymeans of means of a hammer or the like instrument. The other methodinvolves tapping and threading the holes for the receipt of a threadedplug. It has been found that after operation of the engine has occurred,seepage of the lubricating fluid has taken place around the prior artgalley hole plugs, necessitating repair and replacement thereof.

SUMMARY It is a feature of the invention to produce a fluid-tight coverfor apertures in relatively massive parts and a method of making thesame.

The aperture cover of the invention is fabricated by employing asolid-state resistance weld interconnecting a thin walled disc of sheetmetal to the peripheral marginal portion of the exposed face of amassive structure such as an internal combustion engine casting having agalley hole in the exposed surface thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of theinvention will become readily apparent to those skilled in the art fromreading the following detailed description of certain embodiments of theinvention when considered in the light of the accompanying drawings, inwhich:

FIG. 1 is a flow diagram of the method of the invention as applied tothe fabrication of a sealing covering for galley holes formed in thecast blocks of internal combustion engines;

FIG. 2 is a schematic diagram of one form of apparatus and associatedsystem for carrying out the method illustrated in FIG. 1;

FIG. 3 is a fragmentary exploded perspective view of the metal covermember and the part containing the aperture to be covered;

FIG. 4 is a fragmentary sectional view of the assembled compositestructure of the invention illustrated in FIGS. 2 and FIG. 5 is afragmentary sectional view of an assembled composite structure showing amodified form of the invention; and

FIG. 6 is a fragmentary sectional view of an assembled compositestructure showing another modified form of the inventron.

DESCRIPTION OF THE PREFERRED EMBODIMENT As diagrammatically illustratedin FIG. 1, the invention relates to a composite structure of arelatively massive metal part having an aperture to be covered and athin metal sheet covering the aperture and welded thereto, and themethod of making the same utilizing a solidstate resistance weldingtechnique of the thin metal sheet to the peripheral marginal portions ofthe aperture of the relatively massive part. The method involves thetime phased application of a force pulse and a pulse of electricalenergy of a current density within the range of from 500,000 to3,000,000 amperes per square inch of weld or bond interface, typicallyfor an interval of time of the order of 0.5 to 5.5 milli-seconds toeffectively weld the parts together to form an integral unitary article.

In order to properly and adequately explain the method illustrated inFIG. 1, reference will be made to the fabrication of a galley hole coverfor an internal combustion engine block, as illustrated in FIGS. 2through 6, inclusive. The engine block, only a portion of which isillustrated in the drawings, is generally indicated by reference numeral10. The engine block 10 is typically formed of an iron casting andcontains at least one galley hole 12. The galley hole 12 is utilizedduring the production of the engine block 10 to provide a passagewaythrough which lubricating fluids may be conducted during operation ofthe assembled engine. Since, in the operation of the completed engine,the lubricating fluid is pumped through the interior passageways of theengine, the external portion of the galley hole 12 must be covered.Prior attempts at plugging the galley holes by a relatively softermetal, and by the use of a threaded plug, have not been completelysuccessful, since the plugs have allowed a seepage of lubricationtherethrough during operation. In order to completely seal the galleyhole 12, a thin walled metal sheet disc 14 is utilized and welded to theexterior of the engine block 10 in proper overlying relation to thegalley hole 12. It will be appreciated that the welding of the disc 14to the exterior wall of the engine block 10, by normal weldingtechniques, would be extremely difficult to achieve. The weldingprocedure of the invention is illustrated in particular detail in FIG.2. In the procedure illustrated in FIG. 2, the relatively massive engineblock 10 is initially suitably constrained against any lateral movementthereof. Next, the disc 14, which is typically formed of a sheet ofelectrically conductive metal of the order of 0.060 in thickness, to bebonded to the exterior surface of the block 10, is positioned on thelower terminus of a center electrode element 18. Typically, theelectrode element 18 includes a cavity 20 for receiving the disc 14which efiectively constrains the disc 14 from any lateral movementduring the welding process.

The electrode element 18 also includes an inwardly projecting cavity 22which is of a smaller diameter than the diameter of the cavity 20 and isprovided to produce a land 23 which is in contact with the outermarginal edge portion of the inner surface of the disc 14 when the disc14 is placed within the cavity 20.

An adjacent platen member 26 formed of an electrically conductive metalis attached to a force mechanism 40, to be described in greater detailhereinafter, through a support 28 which is insulated therefrom by aninsulating layer 30. It will be appreciated that there is anelectrically conductive path provided between the electrode element 18and the platen member 26. In certain instances, it may be desirable tofabricate the electrode element 18 and the adjacent platen member 26 inthe form of an integral unit.

In operation, the platen member 26 is initially moved toward the engineblock 10, typically by maintaining the engine block 10 in a fixedposition and moving the platen 26 laterally until the disc 14 is incontact with the exterior surface of the block 10 in such a fashion thatthe disc 14 overlaps and covers the hole 12. It will be appreciatedthat, simultaneously with the closing movement of the adjacent platenmember 26 relative to the engine block 10, a series of spaced aparthelical springs 32 are caused to be compressed. The lower ends of thesprings 32 function to exert a downward pressure on an outward ring-typeelectrode element 34 formed to coaxially surround in spaced relation thecenter electrode 18. The center electrode element 18 and the outerelectrode element 34 are electrically insulated from one another by asleeve 36 formed of an electrically insulating material such as Teflon,for example, which not only provides for electrical insulation, but alsoprovides a bearing surface between the electrodes to facilitate relativemovement therebetween.

The force mechanism 40, which includes a pressure transducer, isprovided to apply a pressure pulse on the platen 26, which is, ineffect, superimposed on the initial forces applied by the closing of theplaten 26 adjacent to the block 10. The specific mechanism employed fordeveloping the force by the force mechanism 40 may be of the typeillustrated and described in the patent to A. G. Vang, US Pat. No.

3,059,094, of Oct. 16, 1962. As will become readily apparenthereinafter, when the electrical energy is pulsed through the electrodeelements 18 and 34, a pressure pulse is imposed by the pressuretransducer of the force mechanism 40.

It has been found in practice that forces developed of from the order of2,000 to 3,000 pounds have been employed to produce satisfactory solidstate welds with the described process. These pressures are notconsidered to be critical and may be varied over a rather large range.The pressure imposed on the system can be imposed in many diflerent waveforms, one of which is sinusoidal. As a general rule, the force pulse isapplied before the application of the electrical pulse and does notfully decay until after the decay of the electrical pulse. Typically,the electrical wave form is developed in the secondary winding of apulse transformer 42 which has its primary winding coupled to a weldpower supply 44 through a suitable weld power switch 46. The weld powersupply 44 typically includes a bank of capacitors and a charging circuitwhich are effective to produce an instantaneous source of electricalenergy to the pulse weld transformer 42, as will be explained in greaterdetail hereinafter.

The force mechanism 40 is coupled to a force mechanism power supply 48through a force power switch 50.

The weld power switch 46 and the force power switch 50 are controlled intimed relation to one another by a process control unit 52 which iseffective to energize the respective power switches 46 and 50in such afashion that, typically, the force power switch 50 is energized tocommence the application of the force pulse on the platen 26 and theblock 10, and the disc 14. Then, the control unit 52 is effective toenergize the weld power switch 46 to allow the capacitors of the weldpower supply 44 to discharge and produce an electrical energy pulse inthe primary winding of the pulse weld transformer 42. The secondarywinding of the pulse weld transformer 42 causes a high electrical energypulse between the electrodes 18 and 34, and the disc 14 and the block10. An electrical energy pulse having a current density of the order offrom 500,000 to 3,000,000 amperes per square inch at the fayinginterface between the disc 14 and the block has been satisfactory inachieving the desired results of the invention of obtaining the desiredsolid state resistance weld. In operation of the illustrated embodiment,the force pulse peaks in the order of from 0.5 to 2.0 milliseconds afterthe electrical energy pulse peaks.

It will be appreciated that the outer electrode 34 is effective, inoperation, to apply a contacting pressure on the block 10 to insureproper electrical contact, while the center electrode 18 is effective toproduce the desired bonding pressure to effect the desired force betweenthe disc 14 and the block 10 during the welding procedure.

It has been theorized that the phenomenon involved in the weldingprocess of the invention involves a conversion of electrical energy atthe interface of the disc 14 and the block 10 in a magnitude sufficientto cause the establishment of atomic bonds across the interface,resulting in a solid-state pulse resistance weld. The electrical energypulse applied to the pulse weld transformer 42 follows an electricalpath through the platen 26, the center electrode element 18, which is inelectrical contact therewith, the marginal edge regions of the disc 14,the region of the block 10 adjacent the exterior surface of the aperture12, and the electrode element 34.

It will be noted that the inside diameter of the land 23 of the centerelectrode 18 is larger than the diameter of the hole 12 which willeffectively cause the electrical path, from the center electrode 18 tothe outer electrode 34, to be outwardly of the marginal edge of the hole12, thereby effecting the weld at a distance spaced outwardly of themarginal edge. The formation of the weld in such a location relative tothe hole 12 will militate against any expulsion of metal or oxidesthereof entering the hole 12. In the event of the creation of suchexpulsion during the welding procedure, it will tend to remain in thezone between the mating surfaces of the disc 14 and the adjacent surfaceof the engine block 10 on opposing sides of the weld.

In order to further concentrate and define the weld area of the cover 14and the block 10, certain modified forms of the invention areillustrated in FIGS. 5 and 6. Similar reference numerals are employedfor similar parts with prime designations to distinguish the respectivemodifications.

FIG. 5 shows a modification of the structure illustrated in FIGS. 2, 3,and 4, wherein the disc 14' to be welded to the block 10' to cover thehole 12' is substantially identical with the disc 14' of the firstdescribed embodiment. However, the block 10 has an outwardly projectingannulus 16 around the outer surface of the hole 12' which effectivelycontacts the facing surface of the cover 14. The weld is formed at thefaying interface between the cover 14' and the block 10' with the sameequipment as illustrated in FIG. 2. The modified form of the inventionillustrated in FIG. 5 will enable the current density at the fayinginterface to be concentrated in comparison with the structureillustrated in the previously described embodiment.

Another modified form of the invention is illustrated in FIG. 6, whereinthe cover 14" is covered to produce an annular circumferential groove16' of sufficient diameter to completely encircle the outer surface ofthe hole 12" in the block 10'. Similarly, with respect to the modifiedform of the invention illustrated in FIG. 5, the arrangement of FIG. 6tends to concentrate the current density at the faying interface betweenthe cover 14" and the block 10" and, therefore, more definitively definethe weld shape.

The above described invention is directed to a method for welding thinwalled sheet members to massive bodies. While there is no particularupper limit to the thickness of the thin walled sheet material, it isconsidered that the typical thickness employed for the illustratedembodiments would be of the order of 0.060 inch.

In accordance with the provisions of the patent statutes, 1 haveexplained the principle and mode-of operation of my invention and haveillustrated and described what 1 now consider to represent its bestembodiment. However, I desire to have it understood that the inventionmay be practiced otherwise than as specifically illustrated anddescribed without departing from its spirit or scope.

I CLAIM:

l. A method of welding an electrically conductive seal to the exposedsurface of a massive cast part having at least one hole therein,comprising:

constraining the massive cast part against movement;

disposing the electrically conductive seal in overlying relationship tothe hold in said massive cast part; imposing a peaked force pulse to thefaying interface between said seal and said part to urge the same intointimate contact;

applying a peaked electrical energy pulse to said seal and said part ofa current density within the range of from 500,000 to 3,000,000 amperesper square inch of the faying interface between said seal and said part;and

programming the peak of said electrical pulse and the peak of said forcepulse to be displaced from each other in time by an interval of from 0.5to 2.0 milliseconds to bond said seal to said part to form an integralbonded article.

2. The method defined in claim 1 wherein said electrical energy pulse isapplied as a single pulse.

3. The method defined in claim 2 wherein said electrical energy pulse isof a duration of from 0.5 to 5.5 milliseconds.

4. The method defined in claim 1 wherein the force pulse applied to saidseal and said part reaches its peak amplitude before the electricalenergy pulse arrives at its peak amplitude.

5. The method defined in claim 1 wherein said seal is formed of thinwalled sheet material.

6. The method defined in claim 5 wherein the sheet material is of theorder of 0.060 inch in thickness.

7. The method defined in claim 1 wherein the force pulse and theelectrical energy pulse are applied by means of concentric electrodes,the center electrode applying the force pulse and the center and outerelectrodes cooperatively applying the electrical energy pulse.

1. A method of welding an electrically conductive seal to the exposedsurface of a massive cast part having at least one hole therein,comprising: constraining the massive cast part against movement;disposing the electrically conductive sEal in overlying relationship tothe hold in said massive cast part; imposing a peaked force pulse to thefaying interface between said seal and said part to urge the same intointimate contact; applying a peaked electrical energy pulse to said sealand said part of a current density within the range of from 500,000 to3,000,000 amperes per square inch of the faying interface between saidseal and said part; and programming the peak of said electrical pulseand the peak of said force pulse to be displaced from each other in timeby an interval of from 0.5 to 2.0 milliseconds to bond said seal to saidpart to form an integral bonded article.
 2. The method defined in claim1 wherein said electrical energy pulse is applied as a single pulse. 3.The method defined in claim 2 wherein said electrical energy pulse is ofa duration of from 0.5 to 5.5 milliseconds.
 4. The method defined inclaim 1 wherein the force pulse applied to said seal and said partreaches its peak amplitude before the electrical energy pulse arrives atits peak amplitude.
 5. The method defined in claim 1 wherein said sealis formed of thin walled sheet material.
 6. The method defined in claim5 wherein the sheet material is of the order of 0.060 inch in thickness.7. The method defined in claim 1 wherein the force pulse and theelectrical energy pulse are applied by means of concentric electrodes,the center electrode applying the force pulse and the center and outerelectrodes cooperatively applying the electrical energy pulse.